1. Field Of The Invention
The present invention is directed generally to systems for gravel packing of wells, and more particularly to systems which permit reverse washing of fill encountered as the gravel packing system is run into the well, without tripping the gravel packing system out of the well.
2. Description Of The Prior Art
One typical gravel packing system utilized to perform a circulating gravel pack includes a packer and a crossover setting tool associated with the packer for setting the packer and for controlling the flow of fluids during gravel packing operations. When running such a gravel packing system into a well, one sometimes will encounter sand fill which has infiltrated into the well and blocks the passage down through the well. When this occurs, it is necessary to trip the gravel packing system out of the well, and run a clean out string into the well which is capable of reverse circulating the fill out of the well. Then the gravel packing system must once again be run into the well to perform the gravel packing operation.
One example of such a gravel packing system is that shown in U. S. Pat. No. 4,570,714 to Turner et al. The Turner et al. system utilizes a retrievable packer which is removed from the well with the setting tool after the gravel packing operation is completed.
The assignee of the present invention has also utilized a modified form of the Turner et al. apparatus having a crossover setting tool which initially has an open bore therethrough, and having a washdown shoe at the lower end of the string which receives the wash pipe and which initially permits reverse circulation up through the wash pipe and the work string as the tool is run into the well. If sand fill is encountered as the tool is run into the well, the sand fill can be reversed out without having to pull the work string and gravel packing system. This modified system utilizing a washdown shoe is not capable of washing sand fill from a sump packer.
In wells utilizing a sump packer below the zone to be gravel packed, it is necessary for the gravel packing system to have its lower end sealingly engaged with a bore of the sump packer prior to performing the gravel packing operation. With prior art systems, if sand fill is encountered directly on top of the sump packer, it has been necessary to trip the gravel packing system and its work string out of the well, and run a tapered work string into the well to reverse circulate the sand fill away from the sump packer, then the tapered work string must be tripped out and the gravel pack system again run into the well.
None of the prior art gravel packing systems have been capable of washing sand fill out of a sump packer without first tripping the work string and gravel packing system out of the well and running a special string into the well for purposes of washing the sand fill.